Structure and Conductivity Studies of Scandia and Alumina Doped Zirconia Thin Films

Abstract

In this work, scandia-doped zirconia (ScSZ) and scandia–alumina co-doped zirconia (ScSZAl) thin films were prepared by electron beam vapor deposition. X-ray diffraction (XRD) results indicated a presence of ZrO2 cubic phase structure, yet Raman analysis revealed the existence of secondary tetragonal and rhombohedral phases. Thus, XRD measurements were supported by Raman spectroscopy in order to comprehensively analyze the structure of formed ScSZ and ScSZAl thin films. It was also found that Al dopant slows down the formation of the cubic phase. The impedance measurements affirmed the correlation of the amount of secondary phases with the conductivity results and nonlinear crystallite size dependence.

E-Beam Deposition of Scandia-Stabilized Zirconia (ScSZ) Thin Films Co-Doped with Al

“…The bands at 147, 261, and 635 cm −1 were assigned to the Raman-active modes for the tetragonal phase of ZrO 2 (t-ZrO 2 ), B 1g at 147 cm −1 , E g at 261 cm −1 and A 1g at 635 cm −1 [10,20,[26][27][28]. The cubic zirconia (c-ZrO 2 ) fluorite structure with the Fm3m space group and F 2 g Raman mode symmetry should be centered between 605 and 630 cm -1 , and the peak for Al 2 O 3 is centered at 418 cm −1 [2,10,18,19,23,27].…”

“…The monoclinic phase is retained up to around 1170 • C. The structural changes to a tetragonal phase occur above this temperature. At a temperature of 2370 • C, the tetragonal phase transforms into a cubic fluorite structure, and melts at 2680 ± 50 • C [2,3]. During the transformation from the monoclinic to the tetragonal phase, there is a volume change of around 4%, which can induce defects in the material [4].…”

Structural and Electrochemical Properties of Scandia Alumina Stabilized Zirconia Thin Films

“…The detected peaks at 626 and 628 cm −1 are assigned to the cubic phase. The peaks at 148, 149, 150, 152, 264, 265, 273, 278, 337, 464, 463, 471, and 483 cm −1 are presence of tetragonal phase, and 199, 200, 201, 202, 375, and 382 cm −1 belong to monoclinic phase [16,26,[36][37][38][39][40][41][42][43]. The electrical properties of ScAlSZ thin films were investigated using EIS method, and the Nyquist plots (Figure 4a) were obtained from measurement data.…”

“…Peaks about 202 cm −1 and 346 cm −1 belong to the monoclinic (m-ZrO 2 ) phase [26,36,37]. A weak peak around 535 cm −1 (B g ) and a strong, sharp peak centered around 560 cm −1 (A g ) belong to the rhombohedral (β-ZrO 2 ) phase [16,36,42]. One Raman active vibration F 2g of the cubic (c-ZrO 2 ) phase should be expressed as a broad line peak between 600 and 630 cm −1 [16,17,43].…”

“…Yet, co-doping with alumina gives contradictive results. Other authors found that 5.5 mol.% and higher alumina concentrations do not fully stabilize the cubic phase [15][16][17]. The additional phases exist, reducing the ionic conductivity.…”